My first boss kept a card index of everybody he met in business, supplier or client, noted everything that they said in meetings, a quick word picture of what they looked like: Partner's names, jobs, interests - Children's names, ages etc. etc. and never ever threw anything away. He also used a press cutting service to keep abreast of their careers in trade magazines.
At the time, I was young and had a good memory, but I've always wished I'd done it (especially now, it would be simple on a PC). Now I've retired I'm prepared to admit that I've missed out on substantial business opportunities because I haven't tracked people as they succeeded in their careers.